Wooer captivates one lady-in-waiting (8)
I believe the answer is:
courtier
'lady-in-waiting' is the definition.
(both can mean a royal attendant)
'wooer captivates one' is the wordplay.
'wooer' becomes 'courter' (to woo is to court or pursue romantically).
'captivates' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'courter' going around 'i' is 'COURTIER'.
(Other definitions for courtier that I've seen before include "Monarch's adviser" , "Setter" , "king's follower" , "Rosenkrantz,say" , "Royal adviser" .)